Tommi J. Karkkainen

Acoustic Emission in Power Semiconductor Modules—First Observations

Traditionally, condition monitoring of power semiconductor modules has been based on electrical measurements. Acoustic emission has been utilized for condition monitoring in many other applications, but is an unknown phenomenon in power semiconductor modules. In this paper, the authors present an experimental setup used to show that acoustic emission does occur because of the switching of power semiconductor components. An analysis based on propagation delays is used to determine the source of the acoustic emission.

Sounds from semiconductors - Acoustic emission experiment with a power module

A recent paper showed that the switching operation of a power semiconductor module causes an acoustic emission to take place. In this study, that experiment is repeated using a different kind of acoustic emission sensor. The same conclusion is reached in this stydy as in the previous paper: an acoustic emission takes place as a result of the switching of a power module.

Acoustic emission caused by the failure of a power transistor

The authors show for the first time that acoustic events are related to the failure of transistors. An experimental setup is presented, that was used to make a sample of 26 insulated gate bipolar transistors (IGBT) to fail. The acoustic events in the transistors were monitored. It was discovered that two distinct types of acoustic events are related to the failure. This study complements recent work where it was shown that the switching operation of power transistors causes acoustic emissions to take place.

Time-variant electrical equivalent circuit of a dry bacteriorhodopsin sensor

Modeling the photoelectric response of dry bacteriorhodopsin (bR) sensors has commonly been carried out by following the theory of linear time-invariant systems. However, it has been reported that the time constants of the photovoltage responses of such sensors vary depending on whether the sensor is measured when the incident light is switched on or off. In this paper, we propose an electrical equivalent circuit for dry bR sensors. Unlike the models presented in the literature, the proposed circuit also considers the illumination on the bR sensor. The model is experimentally verified by photocurrent measurements. Further, a new result concerning the photocurrent dependence on the illumination of dry bR sensors is introduced.

Considerations for active condition monitoring in power electronic converters

No generally accepted and widely adopted condition monitoring method currently exists for power electronic converters. Several failure precursors have been proposed for power electronic components. In this paper the authors investigate the requirements for a condition monitoring system for different applications and consider the applicability of previously proposed failure precursors.

Capacitor aging detection in DC-DC converter output stage

One of the most significant reliability issues in switching-mode power supplies is electrolytic capacitor degradation caused by aging. This paper proposes an output voltage transient analysis method to detect capacitor wear-out at the output stage of a step-down dc-dc converter. Changes in the converter output voltage dynamics are evaluated by analyzing the output voltage step response with respect to a decrease in the capacitance. The sensitivity of the method is assessed with respect to parameter variations using an equivalent main circuit model. The feasibility of the presented method is verified by experimental tests using a converter prototype. The results show that the presented method is practical and adequate for detecting capacitor degradation in various operating conditions.

Designing an energy measurement system for an electric vehicle competition - From a student project to a successful race

In this paper, the design and implementation of an energy measurement system for an electric vehicle competition is described. The system consists of PC-based software and a processor-controlled stand-alone measuring unit with an analog front-end, an SD memory card, a radio link, and a USB interface. The work was carried out as a part of a university project course. The designed system was experimentally tested both in the laboratory and in an actual race.

Validation of a time-variant electrical equivalent circuit for a dry bacteriorhodopsin sensor

The photoelectric response of dry bacteriorhodopsin sensors varies depending on whether the incident light is on or off. To model this behavior, we have proposed an electrical equivalent circuit that has a capacitor that varies with the light intensity. In this paper, the proposed model is experimentally validated and found to be appropriate even when the light intensity is changed. The results also confirm that the amplitude of the measured photocurrent changes linearly with the light intensity. The results can be used to correctly analyze and model photocurrent measurements taking the time-variant behavior of the photosensitive biological sensor into account. This knowledge will be useful in sensing systems that utilize photosensitive biological sensors.

Amplifier errors in dry bacteriorhodopsin sensor measurements

Bacteriorhodopsin is considered an important biomolecule for biochemical and technology-oriented studies. The modeling and functionality of bacteriorhodopsin sensors have been extensively studied, but the studies lack the analysis of the errors present in the measurements. Further, the impacts of these errors on photoelectric measurements are mostly unknown. In this paper, we discuss the errors caused by a transimpedance amplifier in the photocurrent measurements on a dry bacteriorhodopsin sensor. This information is especially useful when evaluating the reliability of photocurrent measurements.

Measurement challenges in acoustic emission research of semiconductors

Recently, there have been experiments where the acoustic emission sensors have been used in the investigation of power semiconductor components. In this paper the authors present their observations of measurement related challenges they have encountered while doing such experiments. Special focus is on sensor related difficulties. The main result of this study is that while acoustic emission sensors have limitations and special requirements, performing meaningful acoustic emission measurements in power semicondcutor modules is possible.